A solid laser oscillation device, typically a YAG laser using yttrium (Y) aluminum (Al) garnet (G) crystals as a laser gain medium, is required to cool the laser gain medium to keep the lower energy level less populated, in order to improve the efficiency of laser oscillation.
For instance, a YAG laser doped with ytterbium (Yb) is required to cool the laser gain medium to a temperature not more than 120K, or more preferably, not more than 100K.
Patent Document 1 discloses a laser oscillator. The laser oscillator includes an optical medium, a plurality of first-surface side gain media, at least one second-surface side gain medium, and a cooling unit. The optical medium is transparent to laser light, and includes an incidence medium surface, the first surface, and the second surface facing the first surface. The plurality of first-surface side gain media are excited by excitation light, and amplify laser light while totally reflecting the laser light. The first-surface side media are joined to the optical medium on the first surface of the optical medium. The at least one second-surface side gain medium is, similarly to the first-surface side gain media, excited by excitation light, and amplify laser light while totally reflecting the laser light. The second-surface side medium is joined to the optical medium on the second surface of the optical medium. The cooling unit cools the back surface side of each of the plurality of first-surface side gain media and the at least one second-surface side gain medium, and is disposed so as to cool a plurality of first reflection surfaces and at least one second reflection surface of the gain media.